The Alfalfa Mosaic Virus, named for its typical infestation of alfalfa, has become an increasing problem for those in the hemp and medical cannabis industries. This insect-carried virus can wreak havoc on indoor and outdoor grows alike if proper preventative measures are not observed.
Understanding how Alfalfa Mosaic Virus is transmitted from crop to crop is the first step to combat this unwelcome menace. The second is to understand how Alfalfa Mosaic Virus causes damage to your cannabis plants. The third is creating a strategy to prevent the virus from taking hold and desecrating your crop.
Alfalfa Mosaic Virus is typically transferred from plant to plant by small bugs called aphids. According to Utah State University's Utah Pests Extension [1], this virus "is spread by several species of aphids, and it is unknown if Cannabis aphid is a vector. Aphids acquire the virus from an infected plant and transmit it to hemp by probing leaf tissues".
These aphids can be transferred in many different ways, including (but not limited to);
Another common method is through mechanical transmission. In a grow setting, this will typically be done with improperly cleaned tools, such as scissors. This can be avoided by implementing sanitizing standards and providing each separate grow area with its own tools.
Once transferred from an aphid or mechanical means to a hemp or cannabis plant, Alfalfa Mosaic Virus will begin to have an adverse effect. Though testing can help detect the virus before causing permanent damage, oftentimes it will go unnoticed until visible signs emerge. Tell-tale signs of Alfalfa Mosaic Virus include curling leaves and a bronze discoloration on the leaf that may mimic the appearance of iron excess.
This stress on the plant can damage entire crops, causing the development of seed producing hermaphrodite plants, poor yields, and vulnerability to other damaging inflictions. The later Alfalfa Mosaic Virus is caught, the more damage will be done to the infected crop. If left unresolved, Alfalfa Mosaic Virus can ruin the entirety of a crop. However, the earlier the virus is caught, the sooner it can be remedied. Preemptive testing is one such method that can help save entire crops from ruin, in addition to using predator bugs such as ladybugs and plant-based foliar sprays.
Since information on how Alfalfa Mosaic Virus causes harm to Cannabis is limited, insight can be derived from the over 698 plant species it is known to naturally infect [2-5], which includes potatoes, soybeans, and tobacco. The first step to understanding how a pathogen works typically involves understanding the molecular structure and will provide insight on what biological mechanism the virus interferes with.
In the case of Alfalfa Mosaic Virus, it is composed of a three part genome that combines single-stranded positive-sense RNAs. These RNAs are appropriately named: RNA1, RNA2, and RNA3. RNA1 and RNA2 encode viral replicase proteins, which simply allow for the virus to “reproduce”. RNA3 encodes the movement and coat proteins that provide the basis for infection [6-8].
The coat protein of Alfalfa Mosaic virus allows it to gain access into a plant cell host then causes damage by interfering with importin-a, which is a component of nuclear import pathway [9]. This translates to explaining why this virus is capable of infecting and causing harm to so many plants as the nuclear import pathway is a universal plant function that allows transport across cell membranes [10]. This is akin to stopping you not being allowed to eat. Screwing with how a plant cell takes up nutrients provides an explanation of why the classic bronze discoloration symptoms of Alfalfa Mosaic Virus tend to mimic nutrient deficiency.
Testing can be expensive but is one of the best investments that can be made in a business that depends on successful harvests. Verne Bioanalytics is dedicated to placing the power of testing into your hands. Our i-Test and WE-test models can help remove the guesswork and allow you to move forward with confidence.
Get started on the path to success with Verne Bioanalytics. You can find out more about our state-of-the-art testing models by reaching out using our Contact Us page directly on our website. When you try the technology from Verne Bioanalytics for yourself, you will see how easy setting yourself up for success can be.
[1] Utah State University | Utah Pest Extension. “Alfalfa Mosaic Virus | USU.” USU Extension, https://extension.usu.edu/pests/ipm/notes_ag/hemp-alfalfa-mosaic-virus. Accessed 30 January 2023.
[2] Edwardson JR, Christie RG. Alfamovirus Genus. Alfalfa mosaic virus species. In: Edwardson JR, Christie RG, editors. Viruses infecting peppers and other solanaceous crops. University of Florida Press; Gainesville, FL, USA: 1997. pp. 63–94.
[3] Fletcher JD. New hosts of Alfalfa mosaic virus, Cucumber mosaic virus, Potato virus Y, Soybean dwarf virus, and Tomato spotted wilt virus in New Zealand. N Z J Crop Hortic Sci. 2001;29:213–217
[4] Jasper EMJ, Bos L. Alfalfa mosaic virus. Association of Applied Biologists Description of Plant Viruses N8 229. 1980. [=229 [3 November 2021]
[5] Xu H, Nie J. Identification, characterization, and molecular detection of Alfalfa mosaic virus in Potato. Phytopathology. 2006;96:1237–1242.
[6] Bujarski J, Figlerowicz M, Gallitelli D, Roossinck MJ, Scott SW. Family Bromoviridae . In: King AMQ, Adams MJ, Carstens EB, Lefkowitz EJ, editors. Virus taxonomy: ninth report of the International Committee on Taxonomy of Viruses. Academic Press; Oxford, UK: 2012. pp. 965–976.
[7] Bol JF. Alfalfa mosaic virus and ilarviruses: involvement of coat protein in multiple steps of the replication cycle. J Gen Virol. 1999;80:1089–1102.
[8] van Dun CM, Bol JF, Van Vloten-Doting L. Expression of Alfalfa mosaic virus and tobacco rattle virus coat protein genes in transgenic tobacco plants.
[9] Herranz MC, Pallas V, Aparicio F. Multifunctional roles for the N-terminal basic motif of Alfalfa mosaic virus coat protein: nucleolar/cytoplasmic shuttling, modulation of RNA-binding activity, and virion formation. Mol Plant Microbe Interact. 2012 Aug;25(8):1093-103. doi: 10.1094/MPMI-04-12-0079-R. PMID: 22746826.
[10] https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/nuclear-import
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